So everyone likely to conspire to commit a crime? That's basically paranoia.
While you may have to talk in front of people there is still an element of privacy with telephone calls, you don't expect to be recorded, same with normal speech and other forms of communication. Why should texting and instant messaging be the same? Encrypting essentially allows the same amount of privacy as verbal communication.
Lets not forget the reason the likes of Apple and Facebook started encrypting their messages. The governments (both US and UK) were illegally (not so much in the UK as we glossed over it... We just declared it "unlawful" and changed/are trying to change the law) collecting communications and using other underhand methods to access them. The unencryptable encryption is a self defence mechanism against the (shown) excesses of governments.
Much like a child that spread paint all over the house when the parents weren't looking, they can't be trusted until they show they have changed IMO.
I know we will never agree on this, you are willing to give up your privacy to help your paranoia of the terrorist bogeyman. I'm not however. The fact the government always bring up Terrorists and paedophiles just shows their true hand. They use emotive words like those to scare people, tacking on the end "common" criminality, knowing that most people would say no if it was just to catch "normal" criminals (which it would be used most for) so they use words they know will resonate with a portion of the country unfortunately.